This invention relates to wet filament winding arrangements for manufacturing composite products.
The wet filament winding process is a process in which a reinforcing fiber for a manufactured product is wetted with a molten or a liquid resin by passing the fiber through a liquid resin bath and then delivering it to a rotating mandrel in the wetted state. The wetted fiber is then placed precisely on and held in intimate contact with previously delivered wetted fibers so that when the winding process is complete the part has a very precisely controlled fiber arrangement and uniform fiber-to-resin ratio, producing a part that is constant in composition throughout its volume. The wet resin is then solidified in the manner required by the particular resin, i.e. by cooling a resin that is thermoplastic below its solidification temperature or by setting a settable resin using pressure, heat, ultraviolet light, or a curing agent, if necessary.
Wet filament winding processes have been used to fabricate composite tubing, pressure vessels, and parts having varying cross-sectional areas as well as similar structures and, for specific structural arrangements, wet filament winding can accommodate the insertion of other materials in particular regions of the part such as the ends or intermediate sections. Conventional wet filament winding processes, however, have not been capable of using resins that require temperatures of at least 500.degree. F. to be maintained throughout the entire wet stage of the fabrication process because the resin cools quickly after leaving the liquid resin bath.
Processes for coating fibers with liquid or molten resin to provide a resin reinforced fiber structure which is formed into a continuous fiber reinforced structure having a desired cross-sectional configuration are disclosed in U.S Pat. Nos. 4,168,194, 4,154,634, Re 30,770 and 4,285,749. The arrangements described in those patents, however, would not permit precise placement of wetted fiber on a mandrel as is required for wet filament winding. U.S. Pat. No. 5,529,652 discloses the manufacture of fiber reinforced thermoplastic "pre-pregs" consisting of fibers which have been preimpregnated with resins and then solidified so that the product can be stored for later use in the manufacture of end products. U.S. Pat. No. 5,096,645 describes the fabrication of extruded thermoplastic members that are reinforced by longitudinally extending prestressed elements which are fiber reinforced thermosetting resins that are partially cured in cylindrical dies. The prestressed elements are put in tension and encased in thermoplastic by an extrusion process to produce a solid final product.
U.S. Pat. No. 5,098,496 describes a process for making a postformable composite article containing a heat curable thermosetting polymer by introducing reinforcing fibers continuously into a heat hardenable thermosetting resin and then pulling the polymer composition fiber mixture continuously through a die having a desired shape to form the composite into a continuous product of desired cross-sectional configuration by controlling the pull rate and the die temperature. The polymer composition-fiber mixture is maintained in a gel state so that the formed article can then be cured in a different shape. U.S. Pat. No. 5,425,829 discloses a conventional wet filament winding process for forming composite leaf springs containing glass fibers with a reduced spring rate and uniform stress by replacing a proportion of the glass fibers with plastic fibers. U.S. Pat. No. 4,975,232 describes a process for manufacturing fiber-reinforced linear plastic material formed with a twisted groove on the outer surface to allow for accommodation of an optical fiber by heating a fully cured resin above its glass transition temperature and then inducing a twisted groove.